function [x,y]=pannel(x0,y0,z0,b)

f1=-2*x0^2+2*y0*(b-y0)+60*(z0-15);
f2=4*x0^2+4*y0^2+3600;
f3=sqrt(x0^2+(b-y0)^2+(15-z0)^2);

l20x=(4*f1*x0+f2*x0)/(f2*f3);
l20y=(4*f1*y0-f2*(b-y0))/(f2*f3);
l20z=(-120*f1-f2*(16-z0))/(f2*f3);

x=x0+(25000-z0)*l20x/l20z;
y=y0+(25000-z0)*l20y/l20z;

